Prosecutors on Sunday searched the car of a former Supreme Court chief justice, and the homes and offices of three ex-justices.

During one search, a USB flash drive was seized from the study of former chief justice Yang Sung-tae.

It is the first time in the nation’s 70-year constitutional history that search warrants have been issued and executed for a former head of the judiciary. This is a disgrace.

The former justices are accused of abusing their power by interfering with court rulings in order to win the administration’s favor -- part of an alleged effort to advance legislation on the creation of appeals courts. In fact, however, they did not push any such legislation.

Clearly, nobody should be exempt from judicial proceedings, including search and seizure, but the warrants in question were issued on dubious grounds.

As many as 30 prosecutors have investigated the so-called “trial-bargaining” matter since June. They sought search warrants on dozens of occasions, and the court denied all but a few. Fears of flight or destruction of evidence were not the reason. The charges were not convincing, the court said.

Then it changed course, approving searches targeting the former chief justice and the ex-justices. However, it is unclear what new evidence could have emerged.

The warrants were issued by a prosecutor-turned-judge. Early last month, he was assigned to the job of dealing exclusively with whether to issue or refuse warrants. He had worked as a prosecutor for 11 years before changing his career and becoming a judge in 2009.

Each time a search warrant was denied, prosecutors criticized the court, accusing it of obstructing its investigation, even though Supreme Court chief justice Kim Myeong-soo had effectively asked it to investigate in a statement on June 15.

The decision to issue the search warrant for Yang is seen as a signal that the judiciary has left the door ajar for further investigation. Eyes are now on the court to see whether he will be summoned for questioning.

The warrant for Yang was strangely restrictive, though. It allowed a search only of his vehicle, as the court said there was not enough evidence to raid his home. But prosecutors took advantage of a proviso in the warrant, allowing them to extend their search beyond the car if an item they were looking for was certain to be found in another location. They found the USB flash drive this way after Yang reportedly disclosed its location.

The criteria for these kinds of extended searches are ambiguous. One must ask whether the warrant was issued reluctantly, maybe just for show.

Circumstances seem to have arisen in which Yang met Cheong Wa Dae officials and discussed court trials on issues of interest. If he is found to have broken the law, he should be punished accordingly. But suspicions of “trial bargaining” turned out to be groundless on three occasions, including twice under the current chief justice, through internal scrutiny. Nevertheless, Kim, appointed by President Moon Jae-in and tasked apparently with cleaning up evils in the judiciary under past governments, did not let up.

In an address to mark the 70th anniversary of the judicial branch on Sept. 13, Moon rebuked it as if the trial bargaining were a proven fact. Kim vowed to cooperate with the prosecution more actively.

Few would oppose efforts to eliminate irregularities, but there is concern that they are going too far.

The suspicions are having an impact. People who have lost appeals have insisted that the Supreme Court apologize and nullify past decisions, citing trial-bargaining allegations. The authority of the Supreme Court has been called into question. The independence of the judiciary is being shaken.

Yang denied all suspicions in June at a news conference. Though no incriminating evidence has yet been found, suspicions alone are a disgrace.

The judiciary apparently tried to protect its organization from prosecutorial investigation. It repeatedly refused to submit documents to prosecutors and also turned down requests for warrants.

But it has to cooperate more actively with the investigation. That is the way to restore trust. True self-reform can happen only after all suspicions are cleared away. The warrant for the former chief justice should be understood as a chance for self-reflection. The prosecution, for its part, must avoid feeding any suspicions that it is trying to undermine the judiciary.